Laser annealing using laser light is carried out as a part of a manufacturing method which is a low temperature process for a thin film transistor used for a pixel switch and a drive circuit for a liquid crystal display and an organic EL (Electra Luminescence display. This method irradiates a non single-crystalline semiconductor film formed on a substrate with laser light, thereby locally heating and melting the semiconductor thin film, or heating the semiconductor thin film without melting, and then crystallizes the semiconductor thin film into a polycrystalline film or single-crystalline film in a cooling process. The crystallized semiconductor thin film presents high mobility of carriers, thereby increasing the performance of the thin film transistor. Moreover, the laser annealing treatment applied to the crystalline semiconductor thin film can also carry out modification.
Regarding the irradiation of the laser light, a method of shaping pulse laser light into a rectangular form or a line form, and carrying out overlap irradiation while scanning the pulse laser light, thereby annealing semiconductor is proposed (for example, refer to Patent Literature).
Homogeneous treatment needs to be carried out over the semiconductor film when the laser light irradiates, and control to adjust laser output within a predetermined range, and control to adjust pulse energy within a predetermined range by means of an attenuator is generally carried out so that the irradiating laser light has a stable pulse energy density.